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Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Jan. 01, 2018
Jan. 01, 2015
Accounting Policies [Line Items]        
Cumulative effect of an accounting change     $ 12.2 $ 43.9
Unrealized Gain on Securities        
Accounting Policies [Line Items]        
Cumulative effect of an accounting change     $ (0.8)  
Other Expense [Member] | Accounting Standards Update 2017-07 [Member]        
Accounting Policies [Line Items]        
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification   $ 1.4    
Minimum [Member]        
Accounting Policies [Line Items]        
Finite-Lived Intangible Asset, Useful Life 2 years      
Maximum [Member]        
Accounting Policies [Line Items]        
Finite-Lived Intangible Asset, Useful Life 25 years      
Subsidiaries [Member]        
Accounting Policies [Line Items]        
Ownership Interest in Subsidiary 100.00%